MOSCOW, April 3 (Reuters) - Russia has detained 25
Ukrainians it suspected of preparing attacks in the southern and
central part of the country, the Federal Security Service (FSB)
said in a statement on Thursday.

The detained, who were reported as being members of
ultra-nationalist movements, were planning attacks between March
14 and 17, it said, in Russia's Rostov, Volgograd, Tver, Orel,
Belgorod, Kalmykia and Tatarstan regions.

The press service of the Ukrainian state security service
(SBU) dismissed the report as "nonsense".

The announcement came hours after the SBU said that Russian
security staff had been present at the SBU headquarters aiding
previous authorities during anti-government protests in Kiev in
which more than 100 people were killed.

Russian Rossiya state TV channel aired a video showing
several detained young men, one of them admitting to being a
member of an ultra-nationalist movement.

A website for the NTV channel reported, citing security
services' data, that the detainees were assigned by the SBU to
take pictures of Russia's military equipment near the Ukrainian
border and to establish contacts with radicals inside Russia.

The hints of Russian involvement in Ukraine protests could
further strain ties with the country's former Soviet master,
which annexed the Crimea region after Ukrainian President Viktor
Yanukovich's removal from power, in what has become the worst
East-West standoff since the Cold War.

The FSB denied any involvement in the Ukraine protests.
Russia's RIA news agency quoted it as saying earlier in the day:
"Let these statements be on the conscience of the Ukrainian
Security Service."
(Reporting By Alexei Anishchuk, Editing by Timothy Heritage)